Field of the Invention
The present invention relates to a zoom lens and an image pickup apparatus including the same, which are suitable for an image pickup optical system to be used in an image pickup apparatus using an image pickup element, such as a video camera, a digital still camera, a TV camera, a monitoring camera, an electronic camera, and a film camera.
Description of the Related Art
In recent years, an image pickup apparatus using an image pickup element is increased in functionality, and the entire apparatus is downsized. Moreover, the image pickup element to be used in the image pickup apparatus is increased in sensitivity and size. Accordingly, an image pickup optical system to be used in the image pickup apparatus is required to have high optical performance over the whole range of the image plane, to be small in open f-number, and the like. The image pickup optical system is also required to be as small in aperture diameter of an aperture stop as possible even though a total length of the zoom lens is short and the zoom lens is small in size and f-number.
In U.S. Pat. No. 8,873,155, there is disclosed a five-unit zoom lens including, in order from an object side to an image side, a first lens unit to a fifth lens unit having positive, negative, positive, negative, and positive refractive powers, in which, during zooming, each lens unit is configured to move and an interval between each pair of adjacent lens units is changed.
In U.S. Pat. No. 5,691,851, there is disclosed a six-unit zoom lens including, in order from an object side to an image side, a first lens unit to a sixth lens unit having positive, negative, positive, negative, positive, and negative refractive powers, in which, during zooming, each lens unit is configured to move and an interval between each pair of adjacent lens units is changed.
In U.S. Pat. No. 8,670,187, there is disclosed a three-unit zoom lens including, in order from an object side to an image side, a first lens unit to a third lens unit having positive, negative, and positive refractive powers, in which, during zooming, the second and third lens units are configured to move and an interval between each pair of adjacent lens units is changed.
In order to obtain the zoom lens in which the aperture diameter of the aperture stop is relatively small even though the zoom lens is small in size and f-number, it is important to appropriately set lens structures of a lens system on an object side of the aperture stop and a lens system on an image side of the aperture stop, and the like.